Adega F, Chaves R, Guedes-Pinto H
Laboratório Associado Institute for Biotechnology and Bioengineering, Centre of Genetics and Biotechnology, University of Trás-os-Montes and Alto Douro, P-5001-801 Vila Real, Portugal.
J Genet. 2007 Apr;86(1):19-26. doi: 10.1007/s12041-007-0003-1.
The mammalian family Tayassuidae (peccaries) is confined to the New World and comprises three recognized extant species, white-lipped (Tayassu pecari), collared (Pecari tajacu) and chacoan (Catagonus wagneri) peccaries, which exhibit distinct morphological and chromosomal features. The phylogenetic relationships among the tayassuids are unclear and have instigated debate over the palaeontological, cytogenetic and molecular aspects. Constitutive heterochromatin analysis can be used in understanding the phylogenetic relationships between related species. Here we describe, for the first time, the constitutive heterochromatin (C-positive heterochromatin) of two tayassuid species, Tayassu pecari and Pecari tajacu. We demonstrate that in situ restriction endonuclease digestion with sequential C-banding could be a complementary tool in the study of constitutive heterochromatin heterogeneity in chromosomes of the Tayassuidae. Our characterization of peccary chromosomes suggests that the Pecari tajacu autosomal karyotype is more primitive and has accumulated great diversity in its constitutive heterochromatin. This idea is supported by several other studies that analysed nuclear and mitochondrial sequences of the living peccary species. Finally, the tayassuid X chromosome primitive form seems to be the one of Tayassu pecari.
猪科（西貒）是仅存于新大陆的哺乳动物家族，包含三个已确认的现存物种：白唇西貒（Tayassu pecari）、领西貒（Pecari tajacu）和草原西貒（Catagonus wagneri），它们具有不同的形态和染色体特征。西貒科动物之间的系统发育关系尚不清楚，引发了关于古生物学、细胞遗传学和分子学方面的争论。组成型异染色质分析可用于理解相关物种之间的系统发育关系。在此，我们首次描述了两种西貒科物种——白唇西貒和领西貒的组成型异染色质（C阳性异染色质）。我们证明，原位限制性内切酶消化结合连续C带技术可能是研究西貒科染色体组成型异染色质异质性的一种补充工具。我们对西貒染色体的特征描述表明，领西貒的常染色体核型更为原始，其组成型异染色质积累了很大的多样性。这一观点得到了其他几项分析现存西貒物种核序列和线粒体序列的研究的支持。最后，西貒科的X染色体原始形态似乎是白唇西貒的。
